Hot air furnace



Feb. 17, 1959 R. w. R055 2,873,736

HOT AIR FURNACE Filed July 9, 1956 3 Sheets-Sheet 1 l/VVEA/TOR RIQHARDW. ROSS R. W. ROSS HOT AIR FURNACE Feb. 17, 1 959 3 SheetS Sheet 2 FiledJuly 9, 1956 uvvs/vwk RICHARD W. ROSS HTTDIIVDS Feb. 17, 1959 R. w. R0552,873,736

HOT AIR FURNACE Filed July 9, 1956 5 Sheets-Sheet 3 /M/EA/r0/? RICHARDW. ROSS United States Patent nor AIR FURNACE Richard W. Ross, Winfield,British Columbia, Canada 7 Y Application July 9, 1956, Serial No.596,719

8 Claims. 01. 126-116) This invention relates to improvements in hot airfurnaces.

An object of the present invention is the provision of a furnace havinga main heating chamber mounted on a fire box in order that a wall of theformer comes into direct contact with the fire in the box.

Another object is the provision of a hot air furnace in which air iscirculated in a tortuous passage several times along the walls of a firebox in order to absorb a maximum amount of heat before being directedout of the furnace.

A further object is the provision of a furnace in which air is kept incontact with a fire box for a comparatively long time without thenecessity of increasing the size of the furnace beyond that of the knownfurnaces of a similar capacity.

This furnace includes a fire box spaced from the bottom, side walls, andan end wall of a casing, and a main heating chamber on top of said box.This heating chamber extends the full width of the device and forms thetop of the fire box. In fact, the chamber may be made so that part of itextends downwardly into this box. Air entering the furnace to be heated,moves along the bottom thereof beneath the fire box, up and back alongthe sides of said box, whence it is directed into the main heatingchamber at one end thereof. The opposite end of the main chamber isconnected to a plenum chamber mounted thereabove within the casing. Hotair ducts extend from the plenum chamber to the areas to be heated. Thegases from the fire in thefire box pass outwardly through the rear endthereof and upwardly .to a secondary combustion chamber which is boundedabove and below by the plenum and main heating chambers,

respectively. Means is provided for directing these gases from saidsecondary combustion chamber to a flue. If desired, a passage may beprovided from this secondary chamber upwardly therefrom and back acrossthe top of the plenum chamber. Any fuel may be burned in the fire box,such as coal, sawdust, oil or gas.

Examples of this invention are illustrated in the accompanying drawings,in which,

Figure l is a perspective view of the furnace looking at the backthereof,

Figure 2 is a vertical section taken substantially on the line 22 ofFigure 3,

Figure 3 is a vertical section-taken substantially on the line 33 ofFigure 2,

Figure 4 is a front elevation of the furnace,

Furnace 5 is a horizontal section taken on the line 55 of Figure 2,

Figure 6 is a horizontal section taken on the line 6-6 of Figure 2,

Figure 7 is a horizontal section taken on the line 77 of Figure 2,

Figure 8 is a fragmentary vertical section taken on the line 8-8 ofFigure 3, and

Referring to the drawings, 10 is a hollow base having a flat top 11. Thebase may be formed with two iongitudinal passages 12 and 13, separatedby a central vertical partition 14. Air to be heated is supplied to thepassages 12 and 13 in any suitable manner. In this example, arecirculating duct 18 is connected to the passage 12 at the back of thefurnace, and another duct 19 extends from a suitable source of freshair, such as outside the building being heated, and is connected topassage 13. If desired, a suitable air flow control, not shown,

may be provided in duct 19. Relatively large openings 22 and 23 areformed in the top of the base at opposite sides thereof adjacent thefront end of the furnace; see Figure 7.

A casing 26 extends upwardly from the base 10. 'This casing is formedwith front and rear walls 27 and 28,

side walls 30 and 31, and a top 32. 7

An open-topped fire box 36 is mounted on top of the base 10 and isspaced from the sides and back end of the casing to form side airpassages 37 and 38 and end air passages 39 and 40. By referring toFigure 7, it will be seen that the fire box is located between the baseopenings 22 and 23 and extends to the front end of the base. If coal orwood is to be burned in the furnace, the firebox will be provided withthe necessary grates. How: ever, in the illustrated form of theinvention, an opening 44 is formed in the front wall of the box and hasa collar 45 projecting outwardly therefrom through the casing forreceiving an oil or gas burner unit, not shown. A relatively largeopening 47 is formed in the back wall of the box extending from the topto bottom thereof substantially midway between its opposite sides; seeFigures 6 and 8.

A casing forming a main heating chamber 50 is mounted on top of the firebox. This chamber casing extends laterally and longitudinally to thewalls of the casing, and it forms the top or most of the top of the firebox. If desired, a portion 51 of the bottom of the heating chamber mayproject downwardly into the fire box, as shown in Figures 3 and 8. Theheating chamber is sealed on the fire box and to the casing walls bymeans ofany suitable type of furnace cement.

This chamber is not very deep and is formed at the back end of thebottom thereof with openings 54 and 55, the opening 54 communicatingwith the air passages 37 and 39 therebelo-W, and the opening 55 with theair passages 38 and 40; see Figures 2, 6 and 8. By referring to Figures5 and 9, it will be seen that the back end of the heating chamber isindented to form a smoke channel her with part thereof broken away.

57 extending from the bottom to the top thereof, the end wall 28 of thefurnace casing forming the outer wall of said channel. This channel isdirectly above the opening 47 in the back of the fire box, andpartitions 59 and 60 extend downwardly from the chamber on oppositesides of the box opening to the top of the base 10. These partitions aresealed to the base and to casing wall 28 by a suitable furnace cement.Thus, the channel 57 extends from the fire box opening upwardly to anarea above the main heating chamber which forms a secondary combustionchamber 62, the top of which is formed by a wall 63 extending from sideto side of the casing, and forwardly from the back wall thereof to apoint 64, see Figure 3, spaced from the front wall thereof. The heatingchamber is provided at its forward end with an upwardly extendingprojection 66 which forms a large hot air outlet 67 communicating with aplenum chamber 68 positioned between the wall 63 and the top 32 of thefurnace casing. The projection 66 opens into the plenum chamber at theforward end of the wall 63. Any desired number of hot air ducts 70 mayextend outwardly from the plenum chamber through the side and back wallsof the casing. If it is desired to draw air from the plenum chamber atone or more points considerably above the Patented Feb. 17,1959

furnace, the casing 26 may be extended upwardly to increase theheight ofsaid chamber.

The products of combustion may be removed from the secondary chamber 62in any desired manner. It is, however, preferred to provide a pipe 76extending through the heating chamber projection 66 from said secondarychamber. The forward end of this pipe communicates with'a correspondingopening in the front wall 27 of the casing,'and a pipe 78 may extendupwardly therefrom along said 'front wall to a-horizontal pipe 79 whichextends back across the top 32 of the casing to a smoke pipe 80 whichextends to a flue, not shown.

When this furnace is in use, the fuel is burned in the fire box 36. Theproducts of combustion move out through the opening 47 at the back ofthis box up through the channel 57, into the secondary combustionchamber 62, andthrough pipes 76, 78, 79 and 80 to the line. Atthe sametime, air from the areas being heated is directed into the base passage12 by pipe 13. If it is desired to add fresh air to the system, said airis directed into the base passage 13 by duct 19.- Thus, air entering thefurnace moves along the passages 12 and 13 beneath the base top-11', upthrough the base openings 22 and 23, along the'sides of the box throughpassages 37 and 38, up through the latter and passages 39 and 40 intothe openings 54 and 55 of the main heating chamber 59. This air ispreheated as it moves through the space beneath the fire box, and alongthe sides and back thereof into the heating chamber. This chamber isrelatively large, but not very deep. As the bottom 51 of the heatingchamber forms the top or the main portion of the top of the fire box,the flame in the latter heats the air in said chamber. At the same time,the products of combustion in the secondary chamber 62 heats the mainheating chamber from above and as they pass through the pipe 76. Inaddition to this, the products of combustion in chamber 62 also heat thebottom of the plenum chamber 68. Furthermore, as these products ofcombustion move along pipes 78 and 79, they transfer additional heat tothe air in the plenum chamber. Actually, the air entering the back ofthe furnace at the bottom thereof fol lows a tortuous passage along thebottom of the fire box, back along the sides thereof, up at its backend, forwardly between the top of the fire box and the bottom of thsecondary combustion chamber, up into the plenum chamher and backtherethrough. The gases from the fire also follow a tortuous passageback through the fire box, up past the back end of the main heatingchamber, across the top of the latter, up through pipe 78, and backthrough pipe 79. All the walls of the fire box, excepting the front wallthereof form heat exchange surfaces, while the top and bottom of themain heating chamber and the bottom of the plenum chamber also form heatexchange surfaces. In this way, the air passing through the furnace isdirectly exposed to heat exchange surfaces during practically its entirejourney through the furnace, and it is kept therein for a comparativelylong time. This ensures a maximum transfer of heat within a limitedspace.

What I claim as my invention is:

1. In a hot air furnace, an outer casing having front, back and sidewalls, and a top, an open-topped fire box within the casing extendingfrom the front wall and spaced from the side and back walls thereof,said fire box having a bottom and side and end walls, the end wall ofthe fire box spaced from the outer casing back wall having anoutletopening therein; a shallow relatively wide ens ing forming a-mainheating chamber resting on the top of the fire box and completelyclosing said top, said heating chamber casing projecting beyond the sidewalls and said end wall of the'fire box to the side and back walls ofthe outer casing, a wall spaced a little above the heating chamher andextending'to the'outer casing walls to form therebelow a shallowsecondary combustion chamber above s'aid'heating chamber, and thereabovea plenum chamber within-the outer casing at the top of the latter,passage means extending from the outlet opening of the fire box throughbut completely-separate from the heating chamber to the secondarycombustion chamber, means connected to the secondary chamber to removecombustion gases therefrom, said heating chamber casing having airopenings therein on opposite sides of the passage means and near theouter casing back and side walls, passagemeans extending upwardly fromthe opposite end of the heating chamber casing past the secondarycombustion chamber to the plenum chamber, and 'means connected to theouter casing near the top thereof to remove hot air from the plenumchamber.

2. A hot air furnace as claimed in claim 1 including means for directingair to the air openings of the heating chamber casing, comprising atortuous passage within the outer casing extending along the bottom andthe side walls and an end wall of the fire box.

3. A hot air furnace as claimed in claim 1 including means for directingair to the air openings of the heating chamber casing, comprising twoseparate tortuous passages within the outer casing, each of saidpassages extending along the bottom of the tire box, back along a sidewall thereof, and up along an end wall thereof.

4. A hot air furnace as claimed in claim 3 in which the passage meansfrom the fire box outlet opening runs between the portions of thetortuous passage extending along the end wall of said box.

5. A hot air furnace as claimed in claim 1 in which the means forremoving combustion gases from the secondary chamber comprises a pipeextending from said chamber through the passage means between the mainheating and plenum chambers and out through the outer casing Wall.

6. A hot air furnace as claimed in claimfi including a pipe running fromthe pipe extending through the passage means between the heating andplenum chambers up along the adjacent wall of the outer casing andacross the top of the latter.

7. In a hot air furnace, a hollow base having a top, an outer casingmounted over the base and having front, back and side walls and a top,an open-topped fire box mounted on the top of the base within the outercasing extending from the front and spaced from the side and back wallthereof, said fire box having a bottom and side and end walls, the endwall of the fire box spaced from the outer casing back wall having anoutlet opening therein, the spaces between the side and back walls ofthe casing and the box forming air passages, opening in the base topnear the front wall of the casing between the sides of the box and thecasing side Walls, at least one opening in the base remote from theopenings in the top thereof, air entering the base through thelast-mentioned opening travelling through said base and the top openingsthereof into the air passages, a shallow relatively widecasing forming amain heating chamber resting on the top of the fire box and completelyclosing said top, said heating chamber casing projecting beyond the sidewalls and said end wall of the fire box to the side and back walls ofthe outer casing, a wall spaced a little above the heating chamber andextending to the outer casing walls to form therebelow a shallowsecondary combustion chamber above said heating chamber, and thereabovea plenum chamber Within the outer casing at the top of the latter,passage means extending from the outlet opening of the fire box throughbut completely separate from the heating chamber to the secondarycombustion chamber, means connected to the secondary chamber to removecombustion gases therefrom, said heating chamber casing having airopenings therein near the outer casing back and side 'walls and incommunication with said air passages, passage means extending upwardlyfrom the opposite end of the heating chamber casing past the secondarycombustion chamber to the plenum chamber, and means connected to theouter casing near the top thereof to remove hot air from the plenumchamber.

8. In a hot air furnace, an outer casing having front, back and sidewalls, and a top, an open-topped fire box within the casing extendingfrom the front wall and spaced from the side and back walls thereof,said fire box having a bottom and side and end walls, the end wall ofthe fire box spaced from the outer casing back wall having an outletopening therein; a shallow relatively wide casing forming a main heatingchamber resting on the top of the fire box and completely closing saidtop, said heating chamber casing projecting beyond the side walls andsaid end wall of the fire box to the side and back walls of the outercasing, a Wall spaced a little above the heating chamber and extendingto the outer casing walls to form therebelow a shallow secondarycombustion chamber above said heating chamber, and thereabove a plenumchamber within the outer casing at the top of the latter, passage meansextending from the outlet opening of the fire box through but completelyseparate from the heating chamber to the secondary combustion chamber,said heating chamber casing having air openings therein near the outercasing back and side walls, a hot air duct extending upwardly from theopposite end of the heating chamber casing to the plenum chamber, saidduct being the full width of the heating and plenum chambers, a pipeextending from the secondary chamber through said duct and out of theouter casing, and means connected to the outer casing near the topthereof to remove hot air from the plenum chamber.

References Cited in the file of this patent UNITED STATES PATENTS130,913 Gaston Aug. 27, 1872 400,886 Williams Apr. 2, 1889 661,629Wattles Nov. 13, 1900 709,107 McDonald Sept. 16, 1902 924,815 NelsonJune 15, 1909 1,026,777 Swett May 21, 1912 2,672,858 Iorolemon Mar. 23,1954

